In a known latch needle of this type (see U.S. Pat. No. 3,031,867, Wiederhut, assigned to the assignee of this application, to which German Pat. No. 10 69 812 corresponds), the longitudinal needle slot terminates in the region of the seating surfaces on the upper edges of the side faces of the longitudinal needle slot, and the bottom of this slot, in this region, extends such that it becomes flatter toward the upper edge of the needle shank. In a latch needle of this type, the latch strikes these seating surfaces sharply with its spine, which in time, with latch needles subjected to severe stresses, leads to the destruction of the needle latch and shank.
In order to damp the impact of the needle latch in the rear position and thus avoid damage to the needle and latch, an arrangement has already been designed for a latch needle in knitting machines (see U.S. Pat. No. 4,294,086, assigned to the assignee of this application), such that adjoining a first, short portion of the longitudinal needle slot and containing the slit leading to the lower edge of the needle shank a second longitudinal needle slot portion is provided, which with its length extends beyond the end of the opened latch and which is deeper than half the height of the needle shank. The seating surface for the latch spine is located above the second slot portion. As a result of the cooperation between the needle shank side portions flanking the longitudinal slot and the wedge-like convergent flanks of the seating surface on the latch spine, the side portions are spread apart elastically upon the impact of the needle latch, and friction is produced at the same time at the seating surfaces. The result is a considerable damping of the impact of the latch, which is intercepted in a substantially bounce-free manner, thereby protecting both the latch and the needle shank from damage.
This latch needle has proved to be quite superior in use; however, there is a limit to the amount of damping that can be attained for the needle latch striking the seating surface in its rearward position, because, as the thickness of the needle increases, the elasticity of the needle shank side portions flanking the longitudinal slot necessarily decreases.